Internal brake



March l1, 1930. L. BLACKMOR E 1,750,611

INTERNAL BRAKE Filed Nov. 340, 192'? Patented Mar. ll, 1930 .UNITEDSTATES PATENT oFFlcE LLOYD BLACHIORE, OF HIGHLAND PARK, MICHIGAN,ASSIGNOR TO GENERAL MOTORS CORPORATION, OF DETROIT, MICHIGAN, ACORPORATION OF DELAWARE INTERNAL :BRAKE vApplication :Bled November 80,1927. Serial No. 236,786.

This invention relates yto brakes. The invention is an improvement inrigid shoe brakes particularly intended for use on vehicles but usefulin many other relations, in

fact in any relation where a drum may be carried by a member, therotation of which is to be checked.

The invention aims to provide means Ato `actuate such a brake .whichshall be automatically adjustable to `accommodate for selfactuation ineither direction of rotation of the rotatin member.

Anot er object is to provide a novel brake anchor which shall opeiate inconjunction with the cam to produce effective frictional en agementbetween the drum and the shoes.

s another object the invention provides a shoe construction whichisdesigned to offset the disadvantages consequent upon unequal heateffects which are present in brake shoes of usual construction.

Other objects and advantages will be understood from an examination ofthe accompanying drawing and a reading of the follow1ng specification.

The drawing illustrates what is now regarded as a preferred embodimentof the invention, being, however, illustrative in character only, itbeing understood that changes a0 may be made in structural details.

Figure 1 of the drawing is a view in side elevation of the shoe brake,the drum being y shown in section.

Figure 2 is a view substantially on line 2-2 of Figure 1.

Referring by reference characters to the drawing, numeral 3 representsthe drum. It will be understood that the drum is to be attached to thepart, the rotation of which is to be checked or stop ed. ln vehiclessuch a drum be and prefe 'ably is carried by the wheels. Adjacent thedrum and preferably closing the open end, as is usual in vehiclepractice, is a backing plate 5. In the case of the front wheel backingplate 5 will be carried` by the wheel knuckle while in the case of therear wheel the corresponding plate will be carried by the axle housing.

The backing plate serves to anchor the brake shoes. Secured to thebacking plate,

. sired one `shoe may be of greater length than -the other. In thedrawing, she 23 is shown for the purpose of a shoe anchor, is an anchorbracket 7, its point of attachment bein near the periphery of thebacking plate an at a point such as to secure the desired position forthe brake cam or other actuating means. The anchor bracket may besecured to the backin plate by suitable fastening means 9, of whic threeare shown in the drawing. Pivoted on a '5 pivot pin 11 carried by theanchor bracket are two links 13 and 15. 'Laterally disposed on 60 theanchor bracket 7 are upstanding lugs or stops 17 and 19, the purpose ofthese stops to be later explained.

Within the enclosed space defined by the drum and backing plate are lthebrake shoes 21 and 23. These shoes are preferably of channel shape incross section and extend longitudinally in the form of an arc ofsubstantially the same radius as that of the drum. Their length is suchthat the two shoes when applied to the drum engage almost the entireinner periphery. By this means there is insured a maximum area offrictional engagement between the shoes and the drum. If deas extendingfor somewhatr morel than the ysemi-circumference, and shoe 2l is lessthan a semi-circumference. This arrangement may be adopted to securegreater self-actuation in one^direction of rotation of the drum than inthe other. In the case of vehicles it will obviously be arranged so thatthe self-actuation is greater for forward driving, thereby permittingless pedal movement. In the drawing it will be assumed that clockwiserotation of the drum corresponds to forward driving. Shoe 23 beingrelatively long, when engaged with the drum, tends to rotateclockwiseabout its anchor under the 'iniiuence of drum engagement and this forcesupplements the force exerted mechanically by the cam or other operatingmeans. Shoe 21 similarly becomes self actuating upon a reverse movementof the wheel and drum. Since shoe 21 is relatively shorter it permitsthe use of a relatively longer shoe 23 and thereby facilitates the brakeoperationfor forward driving. ,It will be understood that any otherdesired ratio between the two shoes may be adopted with the resultingchange in self actuation.

With further reference to the channel shaped shoes, it will be seen thatthe web of the shoe carries brake lining represented on the drawing bynumeral 25. It will also be observed that the radial 'de th of thechannel flanges is reduced throng the major part of the channel memberas indicated by numeral 27. The radial depth is increased toward eachend of the shoes. Within the channel adjacent the anchor end is riveteda plate 31 bent over to form an eye to carry pivot pin 35. It will beunderstood that this construction is adopted at that end of each shoeadjacent the anchor pin.- Links 13 and 15 are'pivotally mounted on pins35 so that in moving into drum contact the ends of the shoes move inarcs of short length about fixed pivot 11 as a center. The links 13 and15 are of substantially L-shape, cross each other at the elbow of the L`and extend inwardly as shown at 13 and 15. These ends are held normallyat their maximum movement of separation by a coil spring 37 between thesaid ends 13 and 15. Centering studs 39 may be used on each link toproperly position the spring. The lugs or stops 17 and 19 limit theoutward movement of the links under the action of spring 37 andtherefore determine the released position of the shoes in the vicinityof the anchor.

Adjacent the actuating end of theshoes is a spring 41, the hooked endsof which engage pins 43 transversely positioned in the channels of theshoes. This s ring is to release the shoes from the drum. tops 45 may beprovided with eccentric openings for adjustable rotation on'pins 47mounted as usual in the backing plate to variably determine the brakerelease position of the shoes in the vicinity of the cam or otheroperatin means.

An important feature o the invention re` lates to the cam mounting.Instead of providing a simple rotatable support for the cam shaft 51 inthe backing plate the cam shaft passes through a somewhat elongatedopening 53 in said plate whereby the shaft with the cam may movetransversely in a generally circumferential arc, thus permitting the camto accommodate itself to the self-actuation eect of the drum on theshoes. Such movement of the cam has been heretofore provided by movablymounting the cam on its shaft or by journaling the cam shaft in a linkmounted for swinging. The provision for floating the cam herein shownand described is extremely simple and avoids the additional swinginglink. Each of the side flanges of each shoe adjacent the cam may beprovided with .extensions 55 and 57, oneV outside. and one radiallyinward of the cam shaft. The extensions on one side of each shoe may liein the plane of the side wall, and on the other side of the -shoe theextension may be outthe cam is positioned by the shoes themselves,

having spaced bearings adjacent opposite `side walls of the shoesbetween the upper and lower projections'55 and 57. The cam is thereforefree to fioat so that the manual elfort of brake application is equallydivided between the shoes and whereby full ad vantage may be taken ofthe well understood self-actuation inuence.

When the brake is applied the cam moves the" adjacent ends of the shoesagainst the band and through the tendency of the band to carry'the shoearound with it a certain degree of rotary movement about the pivot 1].results against the resistance of spring 37.

This movement, however, has a radial component so that the' end` of theshoe carrying pin 35 is given a radial thrust toward the drum. Ittherefore follows that in the a plication of the brake a thrust of thebra e shoe towardthe drum is given at both ends of the shoe, thusrendering the action very powerful while preventing any tendency tolock. in the vicinity of the cam as frequently occurs in the case wherethe shoe is positively anchored, and more particularly when the liningnear the anchor has become worn.

The reduced radial dimensions of the channel walls through the majorpart ofthe same andbetween the ends is an im ortant "feature of theinvention. One isadvanta e commonly occurring is inherent in the rigidshoe type of brakea tendency of the shoe to become distorted, to curland to shorten its radius with the result that a part of the shoe failsto contact with the drum resulting in `unequal wear of the lining nearthe anchor action and to give longer life to the lining.

I claim: 1. In a brake, a drum, bra-ke means to fricshown is effectiveto produce a better brake tionallyengage the drum, actuating meanstherefor, a rock shaft carrying said actuating means, means on theadjacent ends of said brake means to support said rock shaft.

2. In a brake, a drum, brake means to frictionally engage the drum,actuating means therefor, a rock shaft carrying said actuating means,means on both sides of the adjacent ends of said brake means to supportsaid shaft.

3. In a brake, a drum, brake means to frictionally engage the drum,actuating means therefor, a rockshaft carrying said actuating means,bifurcated extensions on both sides of each of the adjacent ends of saidbrake means, each of said bifurcated extensions straddling andsupporting said rock shaft at spaced positions.

4. The invention defined by claim 4, the extension on one side of eachof said ends being outwardly bent and overlapping the matingi extensionon the same side of the other en 5. In a brake, a drum, a backingplatehaving a slot, shoes in said drum, anchor means to anchor said'shoes tosaid backing plate. actuating means, a rock shaft rotatable and bodilymovable in said slot, means on the ends of said shoes to support saidrock shaft.

6. In a brake, a drum, brake shoes within said drum, a fixed plate, ananchor bracket on said fixed plate, a pivot pin on said anchor bracket,angular links rotatable on said pin outwardly extended and pivoted tosaid shoes, said links also'inwardly extended, a yielding means betweensaid inward extensions, and stops on said anchor bracket to engage saidshoes under the infiuence of said spring when the brake is released.

7. In a brake, a drum, opposed shoes, actuating means therefor, yieldingmeans between said shoes adjacent said actuating means to release saidshoes, adjustable stop means for one or more shoes adjacent theactuating means, anchor means for said shoes, other releasing means forsaid shoes adjacent said anchor, and other stops adjacent said anchor tolimit the release action of said last named spring.

8. In a brake, a drum, a fixed plate, a fixed anchor pin carried by theplate, crossed levers rotatably carried by the anchor pin, shoes in saiddrum, said levers at their outer ends pivoted to said shoes, springmeans between the inner ends of said levers and stops to limit themovement of said levers under the influence of said spring to determinethe released position of the shoes adjacent the anchor.

9. In a brake, a drum, a plurality of shoes to frictionally engage thedrum, actuating means associated with one pair ofadjacent ends of saidshoes, an anchor at the other pair of adjacent ends, said anchorcomprising a pair of links rotatable upon a fixed pivot l0. Ina brake,a. xed plate, a drum, a plurality of shoes floating in said drum, meansto expand adjacent ends of said shoes against the drum, a plurality oflinks pivoted to a common point on the fixed plate and to theothenadjacent ends of the shoes, said links positioned to give a radialcomponent to the motion of the adjacent ends of the shoes whereby bothends of said shoes are thrust against the drum in the act of applyingthe brake, said links being inwardly extended beyond their pivotalconnection with the fixed plate, yielding means to actuate said linksand release the anchored ends of said shoes, andstops to be engaged bysaid links under the influence of said yielding means.

In testimony whereof I affix my signature.

LLOYD BLACKMORE.

